This invention relates to a method of processing used coolant and more particularly to a method of processing used oil and water emulsion coolant recovered from can bodies in a can manufacturing process to reconstitute and permit the reuse of the used oil and water emulsion coolant.
In the can manufacturing industry, and particularly in the aluminum beverage can manufacturing industry, cans are commonly manufactured in high speed production lines involving the steps of cupping, bodymaking, trimming, washing, printing, internal coating and necking and flanging. In the cupping step, sheet material, such as sheet aluminum, is lubricated with an oil and water emulsion coolant and is then stamped into relatively short height and relatively large diameter cups. In the bodymaking step, each cup is forced by a moving ram through a series of concentric ironing dies that stretch the cup to form a relatively taller height and a relatively smaller diameter can body, approximating the size of the product cans. In both the cupping and bodymaking steps, the sheet material is covered with the coolant to lubricate the sheet material and to dissipate heat generated by the process of stretching and forming the sheet material. After the can bodies have been trimmed, they are carried through a multiple stage can body washer which removes the used coolant and metal fines from the can bodies. The used coolant is then commonly discarded when the used wash water is treated in conventional waste water treatment facilities.
It has now been discovered that used oil and water emulsion coolant recovered from can bodies in a can manufacturing process can be processed for reuse to form reconstituted emulsion coolant by washing the coolant adhering to can bodies off of the bodies with an aqueous solution having a pH less than about 2.0 thereby forming a mixture of the emulsion coolant and the aqueous solution, heating the mixture to an elevated temperature sufficient to break a substantial portion of the emulsion into a first predominately hydrocarbon phase and a first predominately aqueous phase, separating the first predominately hydrocarbon phase from the first predominately aqueous phase, adding a sufficient amount of water to the first predominately hydrocarbon phase to reconstitute the emulsion coolant, adding a sufficient amount of an emulsifying agent or agents to the first predominately hydrocarbon phase and the water to emulsify the first predominately hydrocarbon phase and the water, and filtering the first predominately hydrocarbon phase, the water and the emulsifying agent to form reconstituted emulsion coolant. Additionally, the separated predominately aqueous phase may be heated to a second relatively higher elevated temperature level sufficient to break a substantial portion of any emulsion coolant remaining in the predominately aqueous phase into a second predominately hydrocarbon phase and a second predominately aqueous phase. The second predominately hydrocarbon phase may then be recombined with the first predominately hydrocarbon phase prior to reconstituting the emulsion coolant.